Your textbook describes the classic conservation task in which a 5-year-old child observes equal amounts of liquid in two identical short, wide containers. The child watches as liquid is poured from one short, wide container into a tall, thin container, and is then asked which container holds more water. How does a typical 5-year-old respond?

According to psychologist Jean Piaget, conservation refers to the logical thinking ability that allows a person to complete that a positive quantity will remain the same against adjustment of the container shape or apparent size. This ability develop in the concrete stage at the age of 7 to 11. The conservation task is to test a child's ability to see that some properties are conserved or invariant after an object undergoes a physical transformation. Piaget purposed that children's inability to conserve is due to weakness in the way children think during the preoperational stage. This stage is characterized by children focusing on a single, saliant dimension of the height or length while ignoring other important aspects of the objects.